Adhesion at interfaces between different materials is a critical problem in any coating application. Differences in surface energetics and thermal expansion coefficients frequently lead to poor interfacial bonding. Thin films of adhesion promoters are often coated at the interface. Undoubtedly the most widely known adhesion promoters are silane coupling agents. These are generally organofunctional silanes which are used to improve adhesion between organic resins and mineral surfaces. Since the 1940's, silane coupling agents have been extensively used for better bonding between glass fibers and polymeric resins in the composites field. (E. P. Plueddeman, "Silane Coupling Agents" Plenum Press, New York 1982 ) Additionally, these coupling agents have also seen widespread use in the coatings industry to assist bonding of organic polymers on substrates such as glass.
Brown and co-workers have previously shown that a polystyrene-poly(methyl methacrylate) (PS-PMMA) block copolymer improved fracture toughness at the interface between PS and PMMA by up to a factor of 50. (K. Cho, H. R. Brown, and D. C. Miller, J. Poly. Sci.: Poly. Phys. Ed. 28 (1990) 1699. and H. R. Brown, Macromolecules 22 (1989) 2859.) The minimum thickness of the block copolymer coating to give a plateau toughness was found to be half the lamellar thickness. Although the PS-PMMA blocks described by Brown were effective in improving adhesion between PS and PMMA, they were not particularly effective in improving adhesion between organic polymers, such as PS, and inorganic substrates.
There is a continuing need for inorganic oxide structures which have firmly adhered thereto, organic polymers.